Jack Newfield, the iconoclast columnist whose friends ranged from Robert Kennedy to Muhammad Ali, has died after a brief bout with cancer.

He was 66 and writing columns up until his final weeks.

Newfield died Monday night at New York Presbyterian Hospital-Columbia Medical Center of kidney cancer that had spread to his lungs.

His career as a columnist included 10 years at The Post, and stints at the Village Voice, Daily News and, most recently, the New York Sun.

Newfield also wrote 10 books on subjects ranging from politics to boxing. His targets included ring promoter Don King, the city’s worst landlords and judges – whom he enshrined in an annual list – as well as countless politicians, notably Mayors Ed Koch and Rudy Giuliani.

Newfield was born in Brooklyn in 1938 and grew up rooting for Jackie Robinson and reading Jimmy Cannon and Murray Kempton, the Post columnists he said “made me want to be a journalist.”

After joining the Voice in 1964, he covered the civil-rights movement, was involved in Voice founder Norman Mailer’s 1965 campaign for mayor, and was at the Ambassador Hotel ballroom in Los Angeles when Sen. Kennedy was assassinated in 1968.

Newfield’s honors included a George Polk Award for investigative reporting in 1980, a Gold Typewriter Award from the New York Press Club for his coverage of the 1991 Crown Heights riots, and an Emmy in 1991 for a PBS documentary, “Don King: Unauthorized.”

He also appeared in a cameo in a 1997 HBO biography of King, based on his book, in which he interviewed King, played by Ving Rhames.

Newfield is survived by his wife, Janie Eisenberg, and two children, Joseph and Rebecca.

A funeral service is scheduled for 1:15 p.m. today at Riverside Chapel on West 76th Street. Burial will be at Beth David Cemetery in Elmont, L.I..

Newfield was diagnosed with cancer on Oct. 14 and wrote about his impending surgery five days later:

“These days, I think about what the old trainer Cus D’Amato once told me: ‘The hero and the coward both exactly feel the same emotion of fear. The only difference is that the hero masters that emotion, while the coward capitulates to it and loses his manhood.’ ”